1. Field of the Invention
The present invention is generally related to stimulating nerves and body parts. More specifically, the present invention is related to implantable systems, devices, and methods for stimulating nerves and body parts to achieve therapeutic benefit.
2. Description of the Related Art
Nerves are part of the peripheral nervous system of a human body. They convey sensory signals from skin or organs to the central nervous system and vice versa. Nerves may suffer functional defects due to normal wear and tear, physical injuries, infection, and/or the failure of blood vessels surrounding the nerves. These functional defects may be accompanied by pain, numbness, weakness, and in some cases, paralysis. Other problems may include urinary or fecal incontinence. For example, with urinary incontinence, daily physical activities such as laughing, coughing, and sneezing may result in involuntary urination.
Different tactics have been developed to overcome the above-mentioned problems. One approach involves behavior modification such as urinating more frequently or wearing a protective pad or protective undergarments. In certain social situations, however, individuals may not be able to follow the practice of frequent urination or wearing protective garments. Another approach involves a medical therapy including taking prescribed drugs (e.g. pain medication). This methodology may result in adverse side effects or drug interactions, however, that will ultimately require discontinuation.
Yet another technique for overcoming the above-mentioned problems involves stimulating a nerve having a functional defect by using an electro-medical device that is positioned near a target nerve. One such electro-medical device is commonly referred to as an Implantable Pulse Generator (IPG). An IPG typically includes one or more electrodes, an electrical pulse generator, a battery, and a housing. The electrical pulse generator generates a waveform having a specific shape, form, and frequency range capable of stimulating a target nerve. When the electrodes receive the waveform from the generator, they draw energy from the battery and generate an electric field of suitable strength to stimulate the target nerve.
IPG's have proven to be somewhat effective for stimulating nerves. One of the problems associated with IPG's, however, is that they consume a significant amount of power. Causes of high power consumption include an increase in electrical impedance between the electrodes, or an increase in electrical impedance between the electrodes and the IPG. This may happen due to several factors such as electrode migration, encapsulation of one or more electrodes, and material property changes in the electrodes or body tissue. Material property changes in the electrodes may occur due to a number of factors including chemical changes caused by body fluids being present at the surface of the electrodes, frequent passing of electrical current through the tissue, and normal wear and tear occurring during daily activities.
Higher battery power consumption may also be caused by a phenomenon referred to as “desensitization of stimulus,” whereby the human body responds to an applied external charge by offering a resistance to the applied external charge. The body resists the applied external charge by increasing the stimulation threshold for a target nerve, thereby rendering the earlier stimulus level ineffective. To overcome this problem, a more powerful charge must be generated, which consumes even more battery power. This requires frequent replacement and/or recharging of the batteries.
In other prior art IPG's, it has been observed that the generated electric field spreads widely, affecting untargeted muscles and nerves along with the target nerve. The wide spreading of the electric field significantly reduces the strength of the electrical signal at the target nerve. In order to properly stimulate the target nerve, the strength of the electrical signal must be substantially increased. This requires the waveform generators to draw more power from the battery. Moreover, these prior art IPG's unnecessarily stimulate untargeted nerves and body parts.
Thus, there remains a need for improved devices and methods of stimulating body parts and nerves. There also remains a need for improved implantable systems and devices that more effectively stimulate target nerves and body parts, while not stimulating untargeted nerves and body parts. Furthermore, there remains a need for implantable systems, devices and methods that are less invasive, and that require less power to operate effectively, thereby minimizing the need to replace and/or recharge power sources.